The spindle of a two-for-one twisting or cabling machine is known to be used for the production of twisting, winding yarns or the like from at least two yarns drawn off bobbins, which are generally referred to as an inner yarn or outer yarn.
The bobbin for the inner yarn is often positioned in a so-called spindle pot, which is supported in the region of the axis of rotation of the spindle on a yarn deflection device and is secured by magnets against rotation.
The bobbin of the associated outer yarn is preferably suspended in a creel which is arranged above or behind the two-for-one twisting or cabling machine.
In connection with such two-for-one twisting or cabling machines it has been known for a long time, for example from German Patent Publication DE 41 21 913 A1, to influence the yarn tension of the inner yarn and the yarn tension of the outer yarn on a cording spindle by means of adjusting devices such that the yarns in the cabling point are brought together at the correct yarn tension and speed. This means that the outer yarn is influenced by an outer yarn brake, the braking effect of which is controlled as a function of an inner yarn brake influencing the yarn brake.
In the two-for-one twisting or cabling machine according to German Patent Publication DE 41 21 913 A1 the outer yarn, coming from the outer yarn brake, is introduced centrally into a cording spindle and exits radially at a rotating storage disc which is secured underneath a twisting plate on the cording spindle.
The outer yarn thereby wraps round the storage disc, which balances out yarn tensions caused by fluctuations in the delivery of the yarn, at least partly, before the yarn is moved over the outer edge of the twisting plate into a free yarn balloon, the form and diameter of which is dependent on various factors. Some of these factors are for example the diameter of the storage disc and the twisting plate, the balloon height, the titre of the yarn and the spindle speed of the workstation.
As the optimum adjustment of the aforementioned factors to one another requires a relatively large amount of effort, or is only possible to a limited degree, this effort is often shied away from, as a result of which the form and the diameter of the free yarn balloon are not optimal, which has a very disadvantageous effect on the power consumption of the spindle.
It has therefore already been proposed, for regulating the fluctuations in form and diameter of the free yarn balloon, which are known to be caused by fluctuations in the speed of yarn delivery, to avoid the use of a storage disc arranged underneath a twisting plate and instead to control the yarn tension by means of a balloon limiting pot rotating with the spindle.
By means of European Patent Publication EP 1 167 597 B1 for example a cabling device is known in which a balloon limiting pot prevents the formation of a free yarn balloon. This means that by having a co-rotating pot the outer yarn rotating about the spindle is limited in its radial extension. Furthermore, because of the friction of the running outer yarn on the inner wall of the balloon limiting pot the yarn tension is controlled which corresponds to the effect of using a storage disc.
By using the co-rotating pot designed as a balloon limiter, which absorbs the radial forces of the outer yarn, the yarn tension of the outer yarn is lower than in the cabling device known from German Patent Publication DE 41 21 913 A1 with a storage disc, the cabling device known from European Patent Publication EP 1 167 597 B1 has the disadvantage however that on the one hand the co-rotating balloon limiting pot is exposed to considerable wear from the running outer yarn and the balloon limiting pot also has to be moved along as a rotating mass by the spindle drive. The air friction of the co-rotating balloon limiting pot causes additional losses which have to be compensated by the spindle drive.
In practice no power can be saved with cabling devices, which have a co-rotating balloon limiting pot compared to cabling devices which operate with a storage disc and a free yarn balloon.
A method for operating a spindle of a two-for-one twisting or cabling machine, which is characterized by reduced energy consumption and an associated two-for-one twisting or cabling machine are described in German Patent Publication DE 10 2008 033 849 A1.
In this known method it is proposed to adjust the feeding speed of the outer yarn so that in the region of the twisting plate there can be no storage and the yarn tension of the outer yarn has a value which minimises the diameter of the free yarn balloon circulating the spindle as a function of the geometry of the spindle. This means that in this known method the yarn tension is set so that the adjusted yarn tension is greater than the self-adjusting yarn tension when using a storage disc or a co-rotating pot.
By means of the method described in German Patent Publication DE 10 2008 033 849 A1 the previously valid principle is disproved that a free yarn balloon then only has a marked, unalterable geometry, if it is subjected to storage on a storage disc or is forced through a rotating pot, by means of which a required balancing function is ensured in the twisting or cabling system.
In German Patent Publication DE 10 2008 033 849 A1 by means of the increased yarn tension of the outer yarn before it enters a guiding device, a different launch angle is set on the edge of the twisting plate because of the reduced balloon diameter than the launch angle which is set on the tangential lifting of the yarn from a conventional spindle with a storage disc with the formation of a free yarn balloon or with a yarn balloon forced through a co-rotating balloon limiting pot.
As the required drive power of a spindle, as already explained above, is heavily dependent on the balloon diameter, the reduction of the diameter of the free yarn balloons means that the energy required for forming and maintaining the rotation of the yarn balloon decreases.
In the method known from German Patent Publication DE 10 2008 033 849 A1 however, it is not entirely impossible for the outer yarn to have a storage tendency, for example when starting up the spindle.
In connection with the spindles of two-for-one twisting or cabling machines also yarn rotating devices are known which are designed for example in the form of a blade.
In International Patent Publication WO 2004/057073 A1 for example different such blade-like rotating devices are described for the spindles of two-for-one twisting or cabling machines.
As the spindles of these known two-for-one twisting or cabling machines are not equipped with either a storage disc or a co-rotating pot and also have no controllable device, by means of which the yarn tension of the outer yarn is adjusted to a value at which the diameter of the free yarn balloon rotating around the spindle is minimised as a function of the geometry of the spindle, in the spindles of these known two-for-one twisting or cabling machines free yarn balloons are formed, the form and diameter of which are not at all optimum.
In the case of blade-like rotary devices, as described in International Patent Publication WO 2004/057073 A1, because of fluctuations in the yarn tension, which are determined by fluctuations in the speeds of the yarn supply, often free yarn balloons are formed with a relatively large diameter which has a very disadvantageous effect on the power consumption of the spindle.